1. Field of the Invention
This invention relates to the manufacture of gusseted plastic zipper bags, and particularly to a method for manufacturing such bags with the zipper running transversely to the film feed direction of a vertical form, fill and seal machine on which the bags are formed.
2. Description of the Prior Art
It has heretofore been suggested to provide gusseted zipper bags wherein profile-free sections of the gusset are captured between the zipper profiles. The zipper-free areas of such bags have the thickness of the bag film and hence the mating zipper profiles which capture these areas has to be sufficiently loose fitting to permit such capture which compromises the tightness and security of the zipper closure or requires unduly thin bag walls.
An object of this invention is to provide a method of forming gusseted zipper bags, wherein the portions of the gusset which are captured between the mating zipper elements is relatively thin with respect to the remainder of the bag walls. A further object is to provide such a method which may be practiced on conventional form, fill and seal equipment with relatively minor modification.
The above and other beneficial objects and advantages are attained in accordance with the present invention by cutting transversely aligned windows into a bag making film. The windows are provided at locations corresponding to the gusseted walls of the bags to be formed and aligned with the locations at which profile is to be attached. A carrier web bearing intermittent lengths of zipper is attached to the film with profile-free areas covering the windows. The thickness of the carrier web is relatively thin with respect to the thickness of the bag film